The coenzyme A transphorase system in Clostridium kluyveri.

Koepsell, Johnson, and Meek (1) discovered that cell-free extracts of Clostridium butylicum catalyze the synthesis of butyryl P1 from acetyl P and butyrate. A similar reaction was later observed in extracts of Clost&Gum Icluyveri in which a rapid synthesis of propionyl P from acetyl P and propionate occurs, and the synthesis of higher acyl P compounds from the corresponding fatty acids occurs also, but at a very much slower rate (2). Koepsell, Johnson, and Meek suggested that butyryl P might be formed through a phosphoryl group transfer from acetyl P to butyrate. I The possible r&e of ATP as an intermediary in such a transfer was supported by the demonstration (3) that extracts of C. butylicum catalyze the reversible phosphoryl transfer from ATP to acetate and butyrate; however, an obligatory r&e of ATP or adenosinediphosphate in these reactions was excluded in the C. kluyweri system when it was found that the acyl P interconversion occurs under conditions in which the ATP-acetyl P reaction does not occur (2). Preliminary studies in F. Lipmann’s laboratory carried out in collaboration with M. Doudoroff indicated that the formation of propionyl P from acetyl P and propionate does not occur in the absence of CoA (4). The function of CoA in this acyl P interconversion has since been investigated and the results are reported in this paper. As working hypotheses, two possible reaction mechanisms have been considered. In Scheme I, CoA assumes the rBle of an intermediate phosphoryl group carrier between acetyl P and propionate (Reactions 1 and 2). The over-all Reaction 3 is the experimentally observed result.